Question
1.
2.
3.
4.
Answer (Detailed Solution Below)
Option 4 : $18$
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Detailed Solution
सही उत्तर $18$ है।
Key Points
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prepsnap.in • Part -AQuestion:
If $x^{4} + \frac{1}{x^{4}} = 47$, then the value of $x^{3} + \frac{1}{x^{3}}$ is / यदि $x^{4} + \frac{1}{x^{4}} = 47$ है, तो $x^{3} + \frac{1}{x^{3}}$ का मान है
1.
$12$
2.
$24$
3.
$36$
4.
$18$
Correct Answer: $18$
$x^{2}+\frac{1}{x^{2}} = \sqrt{47+2} = 7$, then $x+\frac{1}{x} = \sqrt{7+2} = 3$, so $x^{3}+\frac{1}{x^{3}} = 3^{3}-3\cdot3 = 18$. / पहले $x^{2}+\frac{1}{x^{2}}=7$, फिर $x+\frac{1}{x}=3$, अतः उत्तर $27-9=18$। Option (c) is the trap for candidates who take $(x+\frac{1}{x})^{3}$ directly without subtracting $3(x+\frac{1}{x})$.
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